Automatic document feeder for a flat bed input device and background plate for use with same

ABSTRACT

A background plate for use with a document feeder and a scanning device having a transparent document support. The background plate includes a plate member and a plurality of support members extending downwardly from the plate member and adapted to support the plate member on the scanning device in spaced relation to the transparent document support.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending applicationSer. No. 09/181,574, filed Oct. 28, 1998, which is itself a divisionalof application Ser. No. 09/041,846, filed Mar. 12, 1998, thespecifications of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present inventions relate generally toward copy document apparatusand, more particularly, to cut sheet print media automatic documentfeeders.

2. Description of Related Art

Automated business machines for producing or reproducing hard copydocuments, such as copiers, printers, telecommunications facsimilemachines, document scanners, and the like, are well known commercially.Ideally, when working with cut sheet print media, a copying apparatusoften includes and automatic document feeder ("ADF") mechanism forautomatically loading and unloading single sheet sequentially to afunctional station where the copying apparatus performs anoperation--e.g., sequentially scans the fed document sheets for copying,faxing, displaying on a computer monitor, or the like. Following theoperation, the ADF then off-loads that sheet and feeds the immediatelyfollowing sheet of the document to the functional station. A sequentialflow of sheets by the ADF and positioning without the necessity ofmanual handling sheets reduces the time required to accomplish thecomplete functional operation. Media which already contains printedmatter (hereinafter referred to generically as a "document") presents aneed for precise alignment to a scanning station in order to generate atrue copy.

Typical commercial ADFs generally require a document sheet pre-pickingmechanism to ensure a single sheet gets to a pick roller, especially insystems having a horizontal input paper tray. Most commercial ADFs forscanners scroll the document page-by-page passed a stationary scan headand into an output tray. However, this makes pre-scanning and othermultiple scanning operations difficult or even impossible, leading todegraded scan output quality. Belt type document feeders, which place adocument onto a flat, transparent, scanning bed, have also beendeveloped. One such system is shown in commonly assigned U.S. Pat. No.5,342,133 (Canfield). A beltless drive system is disclosed in commonlyassigned U.S. Pat. No. 5,788227 (Hexdrix).

Two major problems associated with business machines that include an ADFare the occasionally mis-feed (or "paper jam") and a multiple sheetfeed. Paper jams interrupt operation and require manual correction ofthe problem before the automated conveying can be restarted. Multiplesheet feed can result in a missing page in the copy.

A third common problem is the inadvertent skewing of the document pagein the loading and unloading of paper sheets on the glass of a scanneror copier. Skewing can often lead to a paper jam. A first conventionalmethod is to affix a paper drive mechanism axle to the ADF structure andturn the axle with a motor and gear train or timing belt linkage. Themotor and the linkage are also rigidly mounted to the ADF structure. Thedisadvantage of this method is that it is difficult to balance thenormal force between the two drive rollers. The stiff elastomerdurometer acts as a spring constant and any minor difference in theroller diameter, roller run-out, or roller position relative to the bedwill result in a significant difference in the normal force between thetwo rollers. A second conventional method is to spring load an axle tothe ADF structure, turning the end of the axle with a motor and geartrain or timing belt linkage. The motor is rigidly mounted to the ADFstructure. The linkage moves with the axle and pivots about the motorshaft. The disadvantage is that it becomes substantially impossible tobalance the normal force between the two drive rollers. The linkagegenerates unequal force when moving the drive roller axle in a forwarddirection versus a reverse direction. Because the linkage is positionedat the end of the axle, this unequal force teeters the drive roller axleand results in uneven normal forces. A third conventional method is toagain spring load the axle to the ADF structure, again turning the endof the axle with a motor and gear train or timing belt linkage with themotor and linage moving with the axle. Disadvantages are a difficulty inbalancing the normal force between the two drive rollers and thesusceptibility of a motor suspension to transport shocks (the motorweight far exceeds the required drive roller normal force and thereforerequires a complicated suspension to lift the motor on one end whilemaintaining a balance force to the other end of the axle. A fourthconventional method is to spring load an axle to the ADF structure andturn the axle in the middle. Both the motor and linkage move with theaxle. The disadvantages of this method are that the motor weight farexceeds the required drive roller normal force and therefore requires acomplicated suspension system in the middle of the ADF structure whereit is geometrically constrained and that the motor suspension issusceptible to transportation shocks.

In order to have an ADF with a small workplace form factor (alsosomewhat referred to as a "desktop footprint"), it is desirable to inputand output document sheets from vertically oriented trays. Onevertically aligned paper sheet input mechanism is taught by Hock et al.in related commonly assigned U.S. Pat. Nos. 5,320,436 and 5,326,090.

There is a need for an inexpensive ADF, having a simple paper path andbeing adaptable for hard copy apparatus that employ a flat bed documentscanners.

SUMMARY OF THE INVENTION

In accordance with one invention herein, a modular ADF for use with aflat bed input device, such as a flat bed scanner or flat bed copier,includes a modular chassis including a main chassis disposed between anupper chassis and a lower chassis for defining a complete paper pathonto and off of the flat bed scanner. One advantage of this invention isthat the modular construction facilitates assembly of a chassis thatdefines a complete paper path onto and off of a flatbed scanner in afast and efficient manner. Another advantage of this invention is thatit permits simple plastic injection molding manufacture of the chassisconstructs. Still another advantage is that the use of a minimal numberof foundational ADF units minimizes the tolerance accumulations amongfeatures as well as manufacturing assembly time and skill requirements.Accordingly, the present invention achieves manufacturing cost reductionwhile providing a reliable ADF.

In at least one preferred embodiment, the modular ADF includes anattachment hinge mechanism that advantageously provides precisionalignment of the ADF to the scanner without the use of tools. Thepreferred embodiment also includes a quick connect-disconnect of the ADFto a base unit and a low profile, small footprint, document output tray.The preferred embodiment is configured such that it allows lifting ofthe ADF and direct access to the base unit copying surface to permithand copying such as for brochures and books. The preferred embodimentis also configured such that it eliminates the need for a pre-pickingmechanism to ensure paper gets to a pick roller provides a paper drivemechanism having balanced drive roller normal forces to ensure loadingand unloading paper sheets without skew.

In accordance with another invention herein, the ADF may be providedwith a background plate that includes a plate member and a plurality ofsupport members extending downwardly from the plate member. The supportmembers support the plate member in spaced relation to a scanner so thata document can be fed therebetween for scanning. Although the spacebetween the plate member and scanner is sufficient to allow passage ofthe document, the space is small enough to prevent shadowing effects.The plate member need not be raised when a document is fed onto thescanner, lowered prior to scanning and then raised again sot that thedocument can be removed, as is the case with other background plates. Asa result, ADFs incorporating the present background plate need notinclude a lift mechanism for the plate, thereby reducing component,assembly and repair costs.

The above described and many other features and attendant advantages ofthe present invention will become apparent as the invention becomesbetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Detailed description of preferred embodiments of the invention will bemade with reference to the accompanying drawings. The drawings referredto in this specification should be understood as not being drawn toscale except if specifically noted.

FIG. 1 is a perspective view of an ADF in accordance with one embodimentof a present invention.

FIG. 2 is a rear, left, overhead perspective view of the ADF illustratedin FIG. 1.

FIG. 3 is a rear, right, overhear perspective view of the ADFillustrated in FIG. 1.

FIG. 4 is a front perspective view of a main chassis of the ADFillustrated in FIG. 1.

FIG. 5 is a rear perspective view the main chassis illustrated in FIG.4.

FIG. 6 is a front perspective view of an upper chassis of the ADFillustrated in FIG. 1.

FIG. 7 is a rear perspective view of the upper chassis illustrated inFIG. 6;

FIG. 8A is an exploded, front perspective view of a lower chassis of theADF illustrated in FIG. 1, including an ADF attachment hinge inaccordance with a present invention.

FIG. 8B is a front perspective view of the lower chassis illustrated inFIG. 8A.

FIG. 8C is a fragmentary cross-sectional view of the lower chassisillustrated in FIG. 8A taken along line B--B.

FIG. 8D is a front perspective view of an alternative embodiment of thelower chassis illustrated in FIG. 8A having a paper depressor element.

FIG. 8E is a perspective view of a crossbeam of the attachment hingeillustrated in FIG. 8A.

FIGS. 8F, 8G, and 8H are detail perspective views of retainer hooks forthe attachment hinge illustrated in FIG. 8A.

FIG. 8I is a front, right, low perspective view of the lower chassisillustrated in FIGS. 8A-8C with the attachment hinge illustrated inFIGS. 8A, 8B, 8E, 8F, 8G, 8H mounted thereon.

FIG. 8J is a reverse perspective of detail illustrated in FIG. 8I.

FIG. 8K is a right, rear overhead perspective of the lower chassis withattachment hinge mounted illustrated in FIG. 8I.

FIG. 8L is an enlarged fragmentary perspective view of the hingeattachment illustrated in FIG. 8K.

FIG. 8M is a rear perspective view of the lower chassis illustrated inFIG. 8A.

FIGS. 9A-9G are schematic drawings showing a document sheet loading andunloading sequence.

FIGS. 10A-10B are exploded, perspective drawings of the ADF illustratedin FIG. 1 with a top case.

FIG. 11 is a perspective drawing depicting the orientation of the ADFrelative to a flat bed input device bezel.

FIG. 12 is a perspective detail drawing depicting an input tray paperstop and pick mechanism extracted from the present invention illustratedin FIG. 4.

FIG. 13 is a perspective view showing the paper stop and pick mechanismillustrated in FIG. 12 in situ in a home position.

FIG. 14 is a perspective detail drawing showing the paper stop and pickmechanism illustrated in FIG. 12 in situ in a paper picking position.

FIG. 15 is a rear, left perspective drawing of the main chassisillustrated in FIGS. 4 and 5 showing the mounting of the paper stop andpick mechanism illustrated in FIGS. 12-14.

FIG. 16 is a perspective overhead view of a document sheet backingmechanism in accordance with the invention illustrated in FIG. 10.

FIG. 17 is a schematic elevation side view of the document sheet backingmechanism illustrated in FIG. 16 in the document sheet loading operationcondition.

FIG. 18 is a schematic elevation side view of the document sheet backingmechanism illustrated in FIG. 16 in the document scanning operationalcondition.

FIG. 19 is a schematic elevation side view of the document sheet backingmechanism illustrated in FIG. 16 in the document sheet unloadingoperational condition.

FIG. 20 is a perspective drawing of the paper drive mechanism inaccordance with the invention illustrated in FIG. 10.

FIGS. 21-25 illustrate the mechanical operation of the liftingmechanism.

FIG. 26 is a section view of an ADF in accordance with one embodiment ofa present invention.

FIG. 27 is a side view of the background plate illustrated in FIG. 26.

FIG. 28 is a perspective view of the background plate illustrated inFIG. 26.

FIG. 29 is a plan view of the background plate illustrated in FIG. 26.

FIG. 30 is a plan view of a scanner bezel and transparent supportingsurface that may be used in combination with the ADF illustrated in FIG.26.

FIG. 31 is a cutaway view of the ADF illustrated in FIG. 26.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following is a detailed description of the best presently knownmodes of carrying out the inventions. This description is not to betaken in a limiting sense, but is made merely for the purpose ofillustrating the general principles of the inventions. The scope of theinventions are defined solely by the appended claims.

The detailed description of the preferred embodiments is organized asfollows:

I. ADF with Movable Document Backing

A. Overall Modular Construction

B. Main Chassis

C. Upper Chassis

D. Lower Chassis

E. Attachment Hinge

F. Input Tray Paper Stop and Pick

G. Paper Drive/Document Backing

H. Paper Path

I. Lift Cam Mechanism

II. ADF with Stationary Document Backing

The section titles and overall organization of the present detaileddescription are for the purpose of convenience only and are not intendedto limit the present inventions.

Paper pick and feed drive software and firmware algorithms are wellknown in the art and beyond the scope of the present inventions.Therefore, knowledge of a person skilled in the art is presumed and nodetailed description of such is provided herein nor is such necessaryfor an understanding of the present inventions.

I. ADF with Movable Document Backing A. Overall Modular Construction

Referring now to the drawings and more particularly to FIGS. 1-3, 10 and11, there is shown an automatic document feeder 101 which is constructedin accordance with the preferred embodiment of the present invention andwhich is adapted for use with a flat bed scanner 1101. The automaticdocument feeder 101, will be referred to hereinafter as "the ADF"forsimplicity purposes.

Although in the preferred embodiment of the present invention referenceis made to a flat bed scanner 1101, those skilled in the art willunderstand any type of flat bed input device can be utilized, such as aflat bed copier.

The ADF 101 is modular in nature and generally comprises a set ofassemblies or chassis including a main chassis 401 (FIGS. 4-5), an upperchassis 601 (FIGS. 6-7), and a lower chassis 801 (FIGS. 8A-8D). Thethree chassis 401, 601, and 801 when assembled together form a mediumpath (P) that extends from a medium input tray 403 best seen in FIG. 11,to a medium input tray 803 as illustrated in FIG. 8C. In understandingthe preferred embodiment to the present invention, it will be helpfulthroughout the description that follows, to refer generally to FIGS. 10and 11. FIG. 10 shows an exploded view of the ADF 101 accompanied by andexemplary top case or outer shell 1001, while FIG. 11 illustrates theassembled ADF 101 with the top case 1001 in place relative to a genericscanner 1101.

The three chassis 401, 601, and 801 are each unitray, injection moldedplastic parts adapted for simple assembly. Commercial embodimentdrawings are provided herein; therefore, it will be recognized by thoseskilled in the art that many features shown in the drawings are relatedto the molding process rather than to operational features. Injectionmolding process features are known to be design expedient andimplementation specific; therefore, no further explanation is requiredin order to understand the invention as claimed.

As can be recognized from FIG. 10B, when the ADF 101 is assembled towith the top case 1001 in place, the construct presents to the end-usera simple input document slot 1013, backed by an input tray 403, wherethe stacked document sheets are loaded laterally, print side down, i.e.,rearwardly facing. Note that the document is loaded in a "landscape"orientation regardless of the print orientation on the individualsheets. The only other feature of the assembled ADF construct apparentto the end-user is an output tray 803, protruding upwardly behind theinput tray 403, where collated output document pages are received fromthe internal paper transport mechanism following scanning or copying,for example. Output sheets are then received within a gap between theinput tray 403 backside and the output tray 803 front side, best seen inFIGS. 2 and 3. Any control panel features which may be provided in aspecific implementation, e.g., START and STOP pushbuttons, can also beprovided in an accessible location on the top case 1001. This modularconstruction establishes the complete input-to-output paper path.

B. Main Chassis

Considering now the main chassis 401 in greater detail with reference toFIGS. 4-5, the main chassis 401 to the extent possible for a specificimplementation, is a unitary injection molded plastic part. The mainchassis 401 is provided with all the features to house the operationallyfunctional features of the ADF 101, namely motors, gear trains, shafts,paper picks and rollers, document lift assembly, and electroniccontroller equipment, and to establish an input paper path. Somefunctional features of the main chassis 401 are related to the interfitof the three chassis and paper drive mechanism and, therefore, furtherexplanation of these features is relevant.

As best seen in FIGS. 4-5, the main chassis 401 includes an integrallyformed main chassis shell 405 having a substantially planar base 407. Aninput tray 403 rises upwardly and rearwardly from the base 407. Theinput tray 403 has a document receiving surface 409 that has a concaveshape, in both vertical and horizontal planes. This double-concave shapeassists in both properly aligning the sheets of a multi-sheet inputdocument (not shown) and stiffening the document to facilitate sheetfeeding without jamming. See also, U.S. patent application Ser. No.08/706,032, filed by Hong on Aug. 30, 1996, now U.S. Pat. No. 5,887,239,for an Image-Related Device Having Image-Medium Receiving Tray, and aTray for Same, and a Method for Designing Such Tray, assigned to thecommon assignee of the present invention. More particularly, bypermitting the document to conform to the concave surface shape of theinput tray 403 and having the sheet aligned in the input tray 403 alongits longitudinal edge rather than in the more conventional top or bottomedge first, causes each sheet to stiffen and thus facilitates a cleanindividual sheet pick. See also, U.S. Pat. No. 5,320,436, supra, col.15, starting at line 65. A left input tray stanchion 411 and a rightinput tray stanchion 412, each protruding forwardly from the documentreceiving surface 409, further assist in aligning the sheets of theinput document. As shown only in FIGS. 10A-10B, a sliding paper lengthadjuster, or simply "slider, " 1005 can be mounted to the input tray403.

As will be explained hereinafter in greater detail, the main chassisshell 405 includes three cavity areas 413, 317, and 419 respectivelythat are functionally related. The cavity area 413, is a central cavitythat is disposed between the cavity areas 417 and 419, which arehereinafter called a left side main chassis cavity 417, and a right sidemain chassis cavity 419.

In order to facilitate the specific implementation design expedients,the construct of the shell 405 includes a group of upper right sideinterfit features 415 and a group of left side interfit features 416.The right group of interfit features 415 is disposed on the right sideof the main chassis central cavity area 413, while the left group ofinterfit features 416 is disposed on the left side of the main chassiscentral cavity area 413. The configuration of the groups of interfitfeatures 415 and 416 facilitates the construct of the main chassis 401in a fast and efficient manner. In this regard, as best seen in FIGS.10A-10B, the upper chassis 601 mates between the interfit features 415and 416 permitting the upper chassis 601 to easily drop into the centralcavity area 413 of the main chassis 401. Moreover, the rear side of themain chassis 401 is also configured to matingly engage the lower chassis801. Thus, the lower chassis 801 is easily mounted on the rear side ofthe main chassis 401 by a set of four screws such as screw 1010. In thisregard, as best seen in FIG. 5, a set of molded screw retainer bushings,such as a bushing 50, are provided to align where the lower chassis 801is screw mounted to the main chassis 401.

When the upper chassis 601 is set in place relative to the main chassis401, a sheet feed gap is created between the input tray surface 409 anda rear portion of the upper chassis 601 at about the central cavity area413. Document sheets loaded into the input tray 403 drop sequentially inseriatim through this gap to travel onto the supporting surface of theflat bed input device 1101 as will be explained hereinafter in greaterdetail. Similarly, when the lower chassis 801 is mounted in placerelative to the main chassis 401, a sheet receiving gap is createdbetween the lower chassis 801 and the lower rear of the main chassis401.

Considering now the left side main chassis cavity 417 in greater detailwith reference to FIG. 4, the cavity area 417 is sufficiently large involume to receive therein a left side stepper motor 103. The steppermotor 103 is mounted within the cavity area 413 by and suitable mountingdevices, such as the mounting devices 1010. The cavity area 417 is openoutwardly from the central cavity area 413 in order to facilitate easeof assembling the step motor 103 within the cavity 417.

Considering now the right side main chassis cavity 419 in greater detailwith reference to FIG. 5, the right side cavity area 419 also has asufficiently large volume to receive therein a right side stepper motor301, that is substantially similar in construction to the left sidestepper motor 103. The right side stepper motor 301, like the left sidestepper motor 103 is mounted within the cavity area 419 by conventionalmounting devices 1010.

As will be explained hereinafter with reference to FIGS. 10A-10B andFIG. 12, other mechanical elements of the ADF 101, such as a gear trainor transmission arrangement 1009, a paper pick 1201 and a paper driveshaft 1203, are coupled to the respective stepper motors 103 and 301 ina conventional manner which is well known to those skilled in the art.It is sufficient to note however, that the stepper motors 103 and 301are sequenced in operation by a controller 1003. The controller 1003, asbest seen in FIG. 10B is configured in the form of a printed circuitboard having electrical cabling indicated generally at 1007 thatinterconnects electrically the controller 1003 with the motors 103 and301 as well as other electrical components in the ADF 101. The printedcircuit board is dimensioned to be received within a front cavity area421 of the main chassis 401.

C. Upper Chassis

Considering now the upper chassis 601 in greater detail with referenceto FIGS. 6 and 7, a main cross beam 603 is positioned to traverse themain chassis first cavity 413 parallel to the input tray 403 (FIGS. 1-3and 10). A left side cantilever 607 and a right side cantilever 608extend forwardly from each end of the cross beam 603. Each cantilever607, 608 is provided with interfit features along the lower and sideedges thereof, or as otherwise necessary for a particularimplementation, which mate with the main chassis interfit features 416,415, respectively. Again, it is important to note that the upper chassis601 is a unitary injection molded plastic piece part; molding featuresand interfit features will be specific to a particular designimplementation. The upper chassis 601 is also secured to the mainchassis 401 with conventional fasteners 1010 as shown in FIGS. 10A-10B.

As shown in FIG. 7, the rear of the cross beam 603 is provided with aplurality of protruding fins 605. When the upper chassis 601 is mountedinto the main chassis 401, the fins 605 are in close proximity to theinput tray surface 409 as seen in FIG. 3. When a document is loaded intothe input tray 403, the document sheets are held between the input traysurface 409 and the upper chassis fins 605.

Molded leaf spring features 609, 610 are provided to retain a transfershaft 2003 (FIG. 20) using bushings 625, 626 as shown in FIG. 16. Aseparator shaft 628 (FIG. 9A) is mounted to the upper chassis 601 usingmolded capture bearings and a bushing (not shown) and another moldedleft spring 622 (FIG. 7) provided to retain a bushing (not shown). Theseparator shaft 628 bears a fixedly mounted central paper separatorwheel 631 (FIG. 9A). One end of the separator shaft 628 is coupled to amotor (not shown in this FIG.) via gearing 633 (FIG. 2) and is drivenduring a paper feed cycle.

A spring retainer 611 (FIG. 6A) holds a compression spring (not shown).As shown in FIG. 10A, a tray sensor 701 and a pick sensor 703 as wouldbe known in the art.

D. Lower Chassis--Output Tray

The lower chassis 801 is shown in further detail in FIGS. 8A-8L, alongwith a quick release attachment hinge 821. The entire lower chassis 801is a unitary injection molded plastic part. Like the input tray 403, andas best seen in FIG. 8C, a document output tray 803 has a surface 805that provides a shallow concave curvature in a short height formfactor--in the dimensional region of half the paper width, e.g.,approximately one-half that of an A-size to legal size paper sheet equalto about 4.25 inches. Again this takes advantage of paper stiffnessinduced when it is shaped into a semi-cylindrical form along itslongitudinal axis. Thus, the embodiment can have a lower height formfactor that no longer needs to support a remaining half of a documentsheet by requiring such well known prior art mechanisms as output traypull-out extensions, wire frame clips, or the like. Returning to FIGS.8A and 8B, an upper chassis left stanchion 807 and an upper chassisright stanchion 808 are integrally molded parts of the lower chassis801, protruding forwardly from the output tray surface 805. As shown inFIG. 10A, the two stanchions 80, 808 are used for mounting the lowerchassis 801 via appropriately molded interfit features to the mainchassis 401 wit fasteners 1010 any suitable known on proprietary type.

Along the lower edge of the output tray 803, a document sheet outputguide and shelf 809 extends forwardly. Output tray paper guide fins 811protrude upwardly from the shelf 809 to lift the leading lateral edge ofa sheet of output paper, directing it to follow along the output traysurface.

As best seen in FIGS. 2 and 3, the output tray 803, like the input tray403, has a substantially vertical orientation. The gap between the twotrays 403, 803 provides access for retrieval of the collated outputdocument sheets.

In an alternative embodiment as depicted in FIG. 8D, a paper depressor813 is added to the central region of the surface 805 of the output tray803. To mount the paper depressor, low extremities 815 are formed tosnap-fit to the paper pick and stop shaft 1203 (as shown in FIG. 15).The paper depressor 813 is made of a low friction material such ascommercially available Cycoloy™, made by the General Electric company ofOne Plastics Avenue, Pittsfield, Mass. 01201. This design has beenproven to work reliably for plain papers from 16-pound to 24-pound typesat any acute angle less than forty-five degrees to vertical as long asthe output tray height is at least one-half the document sheet length.With the paper depressor 813, the paper sheets are forced into acylindrical shape and stiffened. Without the depressor 813, the outputtray angle to vertical should be reclining sufficiently to retain thepaper sheets upright.

E. Attachment Hinge

Considering now the quick release attachment hinge 821 in greater detailwith reference to FIG. 8A, the hinge 821 enables the modular chassis401, 601, and 801 when assembled to be mounted to the flat bed scanner1101 with a precisely aligned document feed path relative to thesupporting surface of the scanner 1101. The hinge 821 facilitates atleast two different ADF/scanner orientations for document scanningpurposes coupled with quick release feature for disconnecting the ADF101 from the scanner 1101. In this regard, as shown in FIG. 8A, thelower chassis 801 serves as a mount for the ADF hinge 821. As shown inFIG. 11, this attachment hinge 821 provides a dual purpose mechanism,both for mounting the assembled three chassis ADF 101 to either acompatible copier or scanner or to a bezel 1101 adapted to overlay sucha copier or scanner flat bed scanning surface and for raising andlowering the ADF off a flat bed bezel without removing of the entire ADFsystem.

Returning to FIGS. 8A and 8E-8H, a crossbeam 823 is provided with a setof hinge axle retainers 825, 826, 827, 828, 829, 830. Axle retainers825, 828, and 830 are rearwardly facing and axle retainers 826, 827, and829 are forwardly facing. As seen in FIGS. 8B and 8C, the lower chassis801 is provided with three axle casings 831, 832, and 833. Turning toFIG. 8A, the lower chassis attachment hinge axles 834 are provided toswivel mount the attachment hinge 821 to the lower chassis 801 in theshown manner via the axle retainers 825-830 and axle casings 831-833with each of the axle casings riding an axle between a complementarypair of reversed-facing axle retainers, e.g., the casing element 831 isbetween retainer elements 825 and 826; see also FIGS. 8I-8L.

As shown in FIGS. 8A and 8F-8H, a pair of attachment hinge flanges 835are mounted to the attachment hinge 821 by suitable fasteners 1010 anddepend from the crossbeam 823. As shown in FIG. 11, in combination withthe crossbeam 823, the flanges 835 are used to mount the assembles ADFto either a compatible copier or scanner 1101 or to a bezel adapted tooverlay such a copier or scanner flat bed scanner surface. The flanges835 are provided with dimensions sufficient not only to provide asteady, accurate aligning of the ADF, but also with a length sufficientto allow for lifting of the ADF vertically without removing the entireADF from the scanner 1101 or flat bed, such as when the document pagesto be scanner are in a book or magazine. To facilitate this function,the lower extremity of the hook 835 us provided with a flexible hook 837adapted to catch a complementary lip of edge of the bezel or scannerflange receiving slots (see e.g., FIG. 11, sleeve 1103).

As the ADF is swivel mounted to the hinge 821, ADF tilt-up stops areprovided to facilitate use of the ADF. FIG. 8B shows that the bottom ofthe lower chassis output document sheet guide and shelf 809 is providedwith depending ADF tilt-up stops 841. FIG. 8E shows that the crossbeam823 of the attachment hinge 821 is provided with rising protrusions thatform complementary, hinge tilt-up stops 842. The tilt-up stops 841, 842in the preferred embodiment are matched such that a 65-degree rotationupward of the ADF is permitted (see detail plane B--B, FIG. 8B). FIGS.8I-8L depict the interfit of the hinge features with the lower chassisfeatures. FIG. 11 shows the ADF 101 at its upwardly tilted positiverelative to the scanner 1101. Note that this also facilitates mountingthe ADF to a scanner provided with appropriated flange slots or ascanner 1101 with receiving sleeves 1103.

F. Input Tray Paper Stop and Pick

Paper pick and transport mechanisms are also housed by the main chassis401. FIG. 12 shows an input tray paper stop and pick mechanism 1201 inaccordance with the present invention. FIG. 13 shows the paper stopmechanism 1201 mounted in position with respect to the input tray 403with the mechanism in a paper loading, or "home," position; the upperchassis is not shown in position in this drawing. FIG. 14 shows thepaper stop and pick mechanism 1201 mounted in position with respect toinput tray 403 with the paper stop and pick mechanism in a "retracted"position as it would be during a paper picking operation.

Centrally mounted on a paper pick and stop shaft 1203 is a paper pickroller 1205. The paper pick roller 1205, generally having a rubber orgrit wheel surface, is mounted via a fixed bearing hub 1207. A pair ofspaced apart spring loaded paper stop fence devices 1209 are mounted onopposite side of the pick roller 1205. The stops 1209 protrude into thepaper path (P) and support from below a stack of sheets of paper (notshown) loaded into the ADF 101. As an individual sheet is picked fromthe stack by the pick roller 1205, the stops 1209 force of gravity fromthe stack to start a journey along the paper path to the output tray 801as will be explained in greater detail. Once the picked sheet hascleared the stops 1209, the stops 1209 snap back into the their originalresting positions to support form below any remaining sheets in thestack.

The stop fence devices 1209 are mounted on the shaft 1203 and furtherhelp to minimize teetering of the paper stack on the pick roller 1205.Considering now that paper stop device 1209 in greater detail withreference to FIG. 12, each paper stop fence device 1209 includes ahousing 1211, a one-way needle clutch 1213, and a biasing torsinalspring 1215, biasing the device toward its home position as depicted inFIG. 13. The housing 1211 has extending paper stop fence tabs 1217. Thetorosional spring 1215 provides enough force on the housing 1211 suchthat the tabs 1217 can support a number of sheets of a document (e.g.,50 sheets of legal size paper of up to 24-pound type). In operation,when a document is loaded (see arrows labeled "P") into the input tray,face down--i.e., with the print side facing input tray surface 409--thepaper sheets (not shown) have their side edges sitting on the top edgesof the paper stop fence tabs 1217 which are protruding substantiallyhorizontally through aligned apertures 1301 provided in the surface 409of the input tray 403. Similarly, an aperture 1303 is provided in theinput tray surface 409 for the paper contact surface 1206 of the pickroller 1205 to extend forwardly of the input tray 403.

A paper pick drive shaft 1203 connects the paper stop and pick mechanism1201 to a stepper motor 103. Turning briefly to FIG. 15, the mounting ofthe drive shaft 1203 to a motor 103 is made with standard bushings 1501.

As a sheet of paper is center-picked, the force of a moving documentsheet imparted by the pick roller 1205 is sufficient to release theclutch 1213 and push the tabs 1217 out of the way as shown in FIG. 14.The torsional spring 1215 causes the tab 1217 to bounce back to the homeposition after the trailing edge of the paper clears the outermost pointon the tabs. In other words, by adding a paper stop and pick mechanism1201, the present invention takes advantage of the vertical input tray403 in that paper falls into the pick roller by gravity eliminating theneed for pre-picking mechanism.

G. Paper Drive/Document Backing

A paper drive and document backing mechanism is mounted to theunder-carriage of the main chassis 401. FIG. 16 shows an assembled paperdrive 2001 (detailed in FIG. 20) and a document backer 1601, referred toin the assembled combination as a paper pressure mechanism 1611.

The ADF of the present invention uses the technique sequentially loadingand unloading original document sheets onto the scanner flat bed glass1701 (FIGS. 17-19) using a document backing method taught in U.S. patentapplication Ser. No. 08/651,066 (Hendrix et al.), now U.S. Pat. No.5,788,227, supra. In order to provide the highest quality scannedversion, it is desirable to press the document sheets firmly against theglass 1701 of the scanner. The assembly forming a document backer 1601includes a lift plate 1603 is a substantially rigid, planar material,such as a molded ABS plastic. Mounted on the lower surface of the liftplate 1603 is a foam rubber pad 1605, preferably of polyurethane,commercially available from Boyd company of 13885 Ramona Avenue, Chino,Calif., providing a document backing pressure pad for a document sheeton the scanning bed glass 1701 at a scanning station. To the lowersurface tension of the foam pad, a thin plastic film 1607 preferably ofpolycarbonate film, trade name "Lexan," commercially available fromGeneral Electric company of One Plastics Avenue, Pittsfield, Mass.01201, is provided to act as a low-friction contact with documentsheets.

The combination of materials used in the document backer assembly 1601and the lifting of the assembly during loading and unloading of printmedia sheets from the flat bed of a scanner, or bezel, not only reducesfriction, but also minimizes the electrostatic build-up, improvingreliability of sheet feeding.

In the preferred embodiment, the document backing assembly 1601 ismounted to the undercarriage of the main chassis 401 by slipping theassembly through the main chassis first cavity 413. The document backingassembly 1610 is inserted through the first cavity 413 of the mainchassis 401; front hooks 1610, 1612 mate with molded features of themain chassis under carriage toward the front thereof; spring 1614 loadedbushings 1613 are provided to hold the document backing assembly 1601 inmolded features of the main chassis toward the rear thereof, adjacentthe first cavity 413 as shown in FIG. 10A. The present invention solvesthe problem of getting a document sheet between the glass 1701 and theplastic film 1607 by lifting the assembled paper drive 2001 and documentbacker 1601 as the document sheet is loaded and unloaded from the glass.A lift cam mechanism 1609 moves between:

1. a forward position as shown in FIG. 17, lifting the document backingassembly 1601 to permit a sheet of paper to enter between the assemblyand the scanner bed glass 1701 as indicated by arrow 1703;

2. a central position as seen in FIG. 18, dropping the document backingassembly 1601 onto the scanner bed glass 1701, and

3. a rearward position as shown in FIG. 19, lifting the document backingassembly 1601 to permit a sheet of paper to be driven off the scannerbed glass 1701 as indicated by arrow 1613.

The cam lift mechanism 1609 will be described hereinafter in greaterdetail.

FIG. 20 shows detail of the paper drive mechanism 2001. The reversiblestepper motor 301 is coupled to a transfer shaft 2003 via a conventionalgear train, or other transmission, 2005. A pair of paper drive rollers2007, 2008 are mounted on a paper drive roller axle 2009. The paperdrive roller axle 2009 has spring-loaded mountings 2011, 2012 to the ADFmain chassis 401 structure as depicted in FIG. 15. A gear train linkage2013 is used to turn the paper drive rollers 2007, 2008 via axle 2009 atthe approximate midpoint of the axle. The gear train linkage 2013 moveswith the axle and pivots about the transfer shaft 2003. Note that boththe motor 301 and the transfer shaft 2003 is rigidly mounted to the ADFmain chassis 401 structure. As a result of this configuration, thenormal force of the two drive rollers 2007, 2008 is balanced because thegear train linkage force is applied in the middle of the two driverollers and therefore is equally distributed. The balanced normal forceensures loading and unloading of sheets of the document without skew. Inshort then, the spring loaded drive axle 2009 coupled to the systemtransmission system activates the elastomeric drive roller 2007 and 2008to help facilitate the laoding and unloading of a document sheet ontothe supporting surface of the flat bed scanner 1101 without anysubstantial paper skew. The gear train linkage 2013 is used to providemotion to a lift cam during paper loading and unloading to hoist thedocument backer 1601 off the glass (FIGS. 17 and 19).

H. Paper Path

FIGS. 9A-9G depict the dynamics of the paper path established by themain chassis 401, upper chassis 601 and lower chassis 801. In thisembodiment, a bezel 902 is attached to the apparatus 101. FIG. 9A showsthe apparatus 101 in the condition where a document sheet 901 is loaded.The paper stop and pick mechanism 1201 is in the position shown in FIG.13, and the document sheet 901 is resting on the two paper stop and pickmechanisms 1201 and paper pick roller 1205. The lift cam mechanism 1609is in the same position as shown in FIG. 18, with the document backingassembly 1601 in its lowered position.

FIG. 9B demonstrates pertinent apparatus feature positions during apaper pick operation. The paper pick roller 1205 is motor-activated,turning so as to pull the sheet 901 downward into the tray. The sheet901 is fed downward and shaped between the input tray surface 409 andthe upper chassis 601 fins 605. The tabs 1217 of the paper stop and pickmechanism 1201 are moved out of the way by the sheet 901 as describedwith respect to FIG. 12. The leading edge 902 of sheer 901 is directedtoward the drive rollers 2007, 2008. Activation of the drive rollers2007, 2008, turning in rotation that will receive the leading edge 903of sheet 901 and direct it toward the scanning station, also moves thecam mechanism 1609 to its forward position, lifting the document backingassembly 1601 such that the sheet will slip underneath.

During a paper pick cycle, as shown in FIG. 9C, the leading edge 903 ofthe sheet 901 contacts the surface of the glass bed before reaching thedrive rollers 2007, 2008. It has been found that the buckling of thesheet as it impacts the glass 1701 and before reaching the drive rollers2007, 2008 de-skews any offsets of the sheet.

Turning to FIG. 9D, the drive rollers 2007, 2008 drive the sheet ontothe glass 1701. The trailing edge of sheet 901 remains in contact withthe drive rollers 2007, 2008 when the sheet is positioned for scanning.The lift cam mechanism 1609# returns to its center position and dropsthe document backing assembly 1601 onto the sheet 901.

Following scanning, as shown in FIG. 9F, the drive rollers 2007, 2008are driven in a reverse direction from a sheet feed cycle. The lift cammechanism 1609 is moved to its rearward position as shown in FIG. 19,lifting the document backing assembly 1601 to permit a sheet of paper901 to be driven off the glass 1701. The trailing edge of the sheet 901that had been retained under the drive roller 2007, 2008 has now becomethe exit "leading edge" 905 of the sheet. The lower chassis outputdocument sheet guide and shelf 809 receives the exit leading edge 905.The sheet is driven between the output tray drive rollers 1503 (see alsoFIG. 15). The output tray drive rollers 1503 directs the sheet 901upwardly into the output tray 803 where it is retained behind the shelf809 as shown in FIG. 9G. The lift cam mechanism 1609 is returned to itscenter position.

I. Lift Cam Mechanism

Referring now to the drawings and more particularly to FIGS. 9A-G and21-25 there is shown a lift cam mechanism 1609 that facilitates thelifting of an assembled paper drive 2001 and document backer 1601 duringthe laoding and unloading of a document sheet onto the transparent glasssupport surface 1701. In this regard, the lift cam mechanism 1609 solvesthe problem of transporting such a document sheet between the supportingsurface 1701 and the plastic film 1607 during such loading and unloadingoperations.

Considering now the lift cam mechanism 1609 in greater detail withreference to FIGS. 9A-G and 21-25, the lift cam mechanism 1609 generallyincludes a cam linkage indicated generally at 1615, and a differentialgear train arrangement indicated generally at 1617. The cam linkage 1615and the differential gear train arrangement 1617 in combinationfacilitate a passive automatic lifting action of the document backer1601 to substantially reduce friction and electrostatic build up forreliable sheet feeding purposes.

As best seen in FIGS. 21-25, the cam linkage 1617 generally includes anelongated transfer shaft 2003 that is supported for rotational movementbetween a motor plate 1619 and the chassis 401. A pair of transfergears, 8001 and 8002 respectively, are pressed mounted spaced from oneanother on the shaft 2003 to facilitate a lifting action enabled by afree spinning lift cam 8005 that will be described hereinafter ingreater detail.

The transfer gear 8001 has a larger diameter than the transfer gear 8002and is mounted relative to the shaft 2003 so that is engages a motorpinion gear 1621 extending from the drive motor 103. In this manner, themotor pinion gear 1621 translates the rotational drive of the motor 103to the transfer gear 8001 that in turn causes the shaft 2003 to berotated about its axis at a desired rotational speed.

The lift cam 8005 and a free spinning transfer idler gear 8003 aremounted inwardly of the transfer gear 8002 on the shaft 2003. The idlergear 8003 and the lift cam 8005 are slightly spaced from one anotherwith the lift cam 8005 being mounted furthest from the distal end of theshaft 2003. An elongated lift cam pin 8006 is mounted fixedly by wedgingto the lift cam 8005 and extends outwardly therefrom parallel to theshaft 2003. Mounted to the distal end of the lift cam pin 8006, is afree spinning lift cam composite gear 8004, having a small diameterportion and a large diameter portion. The small diameter portion engagesthe idler gear 8003 and the large diameter portion engages the transfergear 8002.

In order to move a document onto and off the scanner bed glasssupporting surface 1701, is free spinning drive roller 2007 is pressedmounted to a drive shaft 2009 having a press fitted drive gear 8008mounted to its distal end. The drive shaft 2009 is mounted spaced fromand parallel with the transfer shaft 2003 and is supported between themotor plate 1621 and a free spinning cluster housing 8010. The clusterhousing 8010 mounted inwardly of the drive gear 8008 and is supported onand between the transfer shaft 2003 and the drive shaft 2009. Thecluster housing 8010 has fixed thereto and elongated housing pin 8009that extends outwardly therefrom in a plane parallel with the shafts2003 and 2009. A free spinning cluster housing composite gear 8007 ismounted on the pin 8009 between the shafts 2003 and 2009. The compositegear 8007 includes a large diameter portion that engages the drive gear8008 and a small diameter portion that engages the transfer idler gear8003 to further facilitate a lifting action as will be hereinafterdescribed.

As best seen in FIGS. 24-25, the lift cam 8005 includes a pair of spacedapart stops 8005A and 8005B that limit the movement of the lift cam 8005as will be explained hereinafter in greater detail.

Considering now that the operation of the lift cam mechanism 1609 withreference to FIGS. 9A-G and 21-23, the lift cam 8005 begins in a downposition as best seen in FIG. 21. As the motor pinion gear rotates in aclockwise direction in engagement with the transfer gear 8001, thetransfer gear 8001 impacts a counter clockwise rotation to the transfershaft 2003. The transfer shaft 2003, in turn, causes the lift cam 8005to lift and to move to a final lifted position as shown in FIG. 22.

More particularly, as the transfer gear 8002 is fixed to the shaft 2003,the gear 8002 rotates in the same counter clockwise direction and at thesame rotational speed as that of the shaft 2003. The idler gear 8003,however, remain as in a fixed position due to the friction between thedrive roller 2007 and the scanner glass bed 1701. In this regard, theidler gear 8003 locks the gear train of gears 8003, 8007 and 8008. In alike manner as the gear train of gears 8003, 8008 and 8009 is fixed, thedrive shaft 2009, its associated drive roller 2007 and cluster housing8010 also remain fixed in their respective positions. However, the freespinning lift cam composite gear 8004, rides along the transfer gear8002 and the idler gear 8003, and rotates in response to cause the liftcam 8005 and lift cam pin 8006 to move in unison, pivoting in aclockwise direction relative to the transfer shaft 2003.

Once the lift cam 8005 has moved to its final lifted position asillustrated in FIG. 22, the drive roller 2007 starts driving thedocument forward. More particularly, the drive roller 2007 impartsmotion to the document in the following manner. Motion of the lift cam8005 is inhibited by the stops 8005A and 8005B that are wedged on thelift plate 1603. With the lift cam in a fixed position, the lift camcomposite gear 8004 continues to rotate on pin 8006 in a clockwisedirecting that now in turn, imparts a rotational motion to the geartrain comprising gears 8003, 8007 and 8008. In this regard, the gear8003 is rotated in a counter clockwise direction, which motion iscoupled to the drive gear 8008 via the clockwise motion of gear 8007about pin 8009. From the foregoing, it should be understood that thedocument is now pulled forward under the frictional force of the driveroller 2007. The drive roller 2007 rotates in a counter clockwisedirection due to the cluster housing 8010 being held in a fixedposition, while the gear 8007 rotates about pin 8009 to impartrotational motion to drive gear 8008 and shaft 2009.

After the document has been moved into a proper position for scanning,the lift cam 8005 is moved to its original down position as illustratedin FIG. 21. In this regard, the transfer shaft 2003 starts to rotate inan opposite clockwise direction, that in turn, causes the transfer gear8003 to rotate in the same clockwise direction. The lift cam compositegear 8004 riding along gears 8002 and 8003 rotates in an oppositedirection causing the lift cam 8005 and its associated pin 8006 to pivoton the transfer shaft 2003. Motion of the drive roller 2007, drive shaft2009 and the cluster housing 8010 remain fixed as no rotation motion isimparted via gears 8007 and 8008. IN this regard, it should beunderstood that as the motor pinion gear rotates in a counter clockwisedirection, it imparts a clockwise motion to the transfer shaft 2003 viathe transfer gear 8001. The rotation of the transfer shaft 2003 causesthe transfer gear 8002 to rotate in the same direction at the samerotational speed, while the idler gear 8003 remains in a stationaryposition. Again, the friction between the drive roller 2007 and thedocument locks the gear train comprising the gears 8008, 8007, and 8003.Thereafter, the lift cam 8005 remains in a fixed position while thedocument is scanned.

After the document has been scanned, the lift cam 8005 is lifted topermit the document to be moved off of the scanner glass bed 1701. Inthis regard, the motor pinion gear is rotated in a counter clockwisedirection that in turn imparts a clockwise rotation to the transfershaft 2003 and the transfer gear 8002. That is shaft 2003 rotates viathe engagement of the transfer gear 8001 with the motor pinion gear, andthe gear 8002 rotates as it is fixed to the shaft 2003. As explainedearlier, the friction between the drive roller 2007 and the documentlocks the gear train of gears 8003, 8007 and 8008 in a fixed position.

The lift cam 8005 then begins to lift. The composite gear 8004 freespins on pin 8006 and rides along gears 8002 and 8003 causing the liftcam 8005 and its fixed pin 8006 to pivot about the transfer shaft 2003.The drive roller 2007, and drive shaft 2009 however remain in a fixedposition. In this regard, the housing cluster 8010, and gears 8007, 8008remain fixed thus, no rotational motion is imparted to the drive shaft2009. The final lifted position of the lift cam 8005 is illustrated inFIG. 23, where the stop 8005A and 8005B inhibit further motion by thelift cam 8005.

Once the lift cam 8005 has been lifted to its final position asillustrated in FIG. 23, the document is now ejected out from itssupporting position on the scanner glass bed 1701. In this regard, whilethe transfer shaft continues to rotate in a clockwise direction, thelift cam composite gear 8004 rotates in a stationary position counterclockwise about pin 8006. The rotation of gear 8004 is imparted to gear8007, which is turn rotates the drive gear 8008, drive shaft 2009 anddrive roller 2007 in a clockwise direction. In this manner, theclockwise rotation of the drive roller 2007 moves the document off thescanner bed 1701 in a reverse direction.

After the document has been removed from the scanner bed 1701, thepinion gear rotational direction is reversed, which in turn, causes thetransfer shaft 2003 to rotate in a counter clockwise direction. Thecounter clockwise rotation of the shaft 2003 imparts motion to the liftcam 8005 to return it to a down position. More particularly, thecomposite gear 8004 rotates in a clockwise direction and rides alonggears 8002 and 8003 causing the lift cam 8005 and its associated pin8006 to pivot about the transfer shaft 2003. The friction between thedrive roller 2007 and the glass scanner bed 1701 locks the gear train8008, 8007, and 8003 in a fixed position. The lift cam 8005 comes torest in it down position read for the next document.

From the foregoing, it should be understood by those skilled in the artthat the lift cam 8005 is driven in a predetermined sequence that startswith the lift cam 8005 being positioned in a down position asillustrated in FIG. 21 and ending in the same down position. Thesequence includes:

1. moving the lift cam 8005 upwardly from a down position to an extendedposition that permits the document to be moved onto the scanner bed1701;

2. driving the document onto the scanner bed 1701 via the drive roller2007;

3. lowering the lift cam 8005 to its down position prior initiating ascanning operation;

4. waiting for the document scanning operation to be completed;

5. moving the lift cam 8005 upwardly from the down position to theextended position to permit the document to be moved off of the scannerbed 1701;

6. driving the document in a reverse direction off the scanner bed 1701;and

7. lowering the lift cam 8005 to its down position to wait for anotherdrive/eject cycle.

II. ADF with Stationary Background Plate

The ADF 101 described abvoe and illustrated in FIGS. 1-25 includes adocument backing assembly 1601 that is lifted and lowered during theloading and unloading of a document onto the transparent supportingsurface 1701. Lifting and lowering are accomplished through the use ofthe lift cam mechanism 1609 illustrated in FIGS. 9A-G and 21-25. Asillustrated for example in FIG. 26, an ADF 2100 in accordance with apreferred embodiment of another present invention lacks the documentbacking assembly 1601 and lift cam mechanism 1609 and, instead, includesa stationary background plate 2101. The ADF 2100 is otherwisesubstantially identical to the ADF 101 and common elements areidentified by common reference numerals.

The background plate 2102 is located above the transparent supportingsurface 1701. Referring more specifically to FIGS. 27-29, the exemplarybackground plate 2102 includes a plate member 2104 and a plurality ofdownwardly extending support members 2106a-c that support the platemember on a scanner, such as scanner 1101, abvoe the transparentsupporting surface 1701. The plate member 2104 includes a planar portion2108 and a curved portion 2110. The distance between the plate member2104 and the transparent supporting surface 1701 is large enough toallow a document 901 to be fed on to and off of the transparentsupporting surface without moving the background plate 2102, yet smallenough to prevent shadowing effects. The distance between thetransparent supporting surface 1701 and the bottom of the plate member2104 in the illustrated embodiment is about 1.0 mm at the rearward end2112 and about 0.5 mm at the forward end 2114. The support members2106a-c are sized to provide this spacing.

Supporting the background plate 2102 in this manner provides a number ofadvantages. Most notably, the background plate 2102 need not be raisedwhen a document is fed onto the scanner, lowered prior to scanning, andthen raised again so that the document can be removed. The need for alifting mechanism, such as the aforementioned lift cam mechanism 1609,which includes the two-part lift cam 8005, lift cam pin 8006, compositegear 8004, and transfer gear 8002, is therefore eliminated. The need fora three part document background plate, such as the aforementionedbackground plate 1601, which includes a lift plate 1603, a foam rubberpad 1605, and a low-friction film 1608, is also eliminated. As a result,use of the present background plate greatly reduces component andassembly costs. Assembly costs are further reduced because thebackground plate 2102 is not coupled to the paper drive mechanismillustrated in FIG. 20. This allows the paper drive mechanism to beinserted through the top of the chassis, which is much easier than theprior insertion method that required a number of difficult manipulationsof the chassis so that the paper drive mechanism could be installedthrough the center of the chassis with the chassis tilted upwardly.

Although the exemplary plate member 2104 is supported on the scanner atfour points, there are only three support members 2106a-c in theillustrated embodiment. The reason is as follows. As shown by way ofexample in FIG. 30, a thin polycarbonate label 2116 rests on top of thetransparent supporting surface 1701. The label 2116, which isapproximately 0.5 mm thick, is used to define the left scanning limitand includes indicia that allows user who are not using the ADF toproperly align letter size (A) and European size (A4) documents on thetransparent supporting structure 1701. [Note that legal size (L)documents are fed with the ADF transverse to letter (A) and European(A4) documents and that the legal size (L) documents are scanned in atwo step process.] To offset the 0.5 mm thickness of the label 2116, theheight of support member 2106a, which rests on the label, is 0.5 mm lessthan that of support member 2106b, which rests of the transparentsupporting surface 1701. The height of a fourth support member (shown indashed lines) would be 0.5 mm less than the height of the support member2106c, which also reset on the transparent supporting surface 1701. Inthe illustrated embodiment, however, the thickness of the label 2116 isequal to the height of the support member 2106c, thereby eliminating theneed for a fourth support member. The distances between support members2106a and 2106 b is, of course, sufficient to allow documents such asthe letter size (A) document 901 shown in dash lines to passtherebetween.

The exemplary background plate 2102 also includes an attachment systemthat allows the background plate to be easily secured to the ADFchassis. The exemplary attachment system illustrated in FIGS. 27-29 and31 secures the background plate 2102 to the ADF chassis at four pointsby way of a pair of rearward latch elements 2118 and a pair of forwardlatch elements 2120. The rearward and forward latch elements 2118 and2120 deflect and snap over corresponding rearward and forwardprotuberances 2122 and 2123 (FIG. 31) within the chassis during assemblyand disassembly. In the illustrated embodiment, the rearwardprotuberances 2122 are rectangular, while the forward protuberances 2123are cylindrical. The latch elements 2118 and 2120 respectively includeramps 2126 and 2128 that facilitate assembly. Disassembly requires theuser to manually deflect the latch elements 2118 and 2120 so that theymay be pulled past the protuberances 2122 and 2124. The ease of assemblyand disassembly associated with the present attachment system furtherreduces manufacturing costs and also reduces repair costs.

The exemplary attachment system also allows the background plate 2102 tomove slightly relative to the ADF chassis. Such movement insures thatthe support members 2106a-c will rest on the scanner despite minorvariations in the relative positions of the ADF and scanner and/or minorwarping in the background plate 2102. For example, the ADF chassis maybe configured such that the rearward latch elements 2188, which rest ontop of the rearward protuberances 2122, are free to move about 4 mmabove the protuberances. Additional movement is prevented by the upperstops 2131 (FIG. 31) on the main chassis and the steps 2150 on thebackground plate 2102. The exemplary forward latch elements 2120 includeobround apertures 2130 into which the cylindrical forward protuberances2124 extend. The height of the apertures 2130 is preferably about 1.5 mmgreater than the diameter of the protuberances 2124 so as to tallow forsmall amounts of movement. The small amount of relative movement allowswrinkled sheets to pass through the ADF without jamming and alsoprovides relief for tolerances created by the mating of the backgroundplate 2102 and chassis as well as warping of the background plate.

As illustrated for example in FIGS. 27-29, a pair of spacing tabs 2132are used to restrict the lateral positioning of the forward portion ofthe background plate 2102 to prevent disengagement of the forward latch2120 during shipping.

The exemplary background plate 2102 is provided with a pair of openings2136 (FIG. 28) that allow the drive rollers 2007 and 2008 (FIG. 20) toextend through the plate member 2108, a pair of abutments 2134 on eitherside of one of the openings and a pair of supports 2138 (FIGS. 27-29).The abutments 2134, which are spaced approximately 0.5 mm from theassociated drive roller hub, allow the drive roller to control theposition of the plate. The position of the drive roller is, in turn,controlled by the position of the drive roller axle 2009 which issecured to the chassis with a bushing arrangement.

The supports 2138 are used to prevent excess travel of the drive rolleraxle 2009 caused by forces applied to the drive rollers 2007 and 2008.The drive roller axel 2009 is allowed to move a small distance in orderto compensate for differences in document thickness. The supports 2138and drive roller axle 2009 are positioned relative to one another suchthat the drive roller axle will contact the supports after the driveroller axel moves beyond that distance, thereby preventing disengagementof the drive roller axel from the bushing arrangement.

The rearward regions of the background plate 2102 also includes aplurality of paper size sensor openings 2140 (FIGS. 28 an 29) in apredetermined pattern. The paper size sensor openings 2140 are used bythe scanner to distinguish between letter (A) and European (A4) sizeddocuments. After the document has been fed onto the transparentsupporting surface 1701, the image scanner focuses on the area includingthe paper size openings 2140. The paper size sensor openings 2140 willbe covered in those instances where a letter (A) sized document ispresent. [Note the relative positioning of the letter (A) and European(A4) documents in FIG. 30.]0 This provides the system controller with anindication as to the size of the document being scanned and, because itdoes so with image scanner, eliminates the need for an additionalsensor.

One important consideration associated with the use of the presentstationary background plate 2102, which is preferably formed withplastic materials such as polystyrene, styrene copolymer or HIPS, isstatic electricity. A buildup of static electricity can interfere withmovement of the documents. To that end, and as illustrated for examplein FIGS. 27 and 29, the exemplary background plate 2102 includes agrounding post 2142 that may be connected to a ground, such as theground on the ADF's printed circuit assembly. The grounding post 2142 isprovided with an eyelet 2144 for a screw that is used to connect a draincable (not shown) to the grounding post. Static may be reduced bycombining an anti-static additive with the plastic material which makesthe plastic conductive and allows charges to drain to the grounding post2142. A suitable anti-static additive is the Variant AdditiveConcentrate (product no. CSY9301A) from Clariant/North America. Theanti-static additive is between about 3% and 6%, and preferably about4%, of the plastic/anti-static additive mixture.

In many scanners, such as scanner the exemplary scanner 1101, thetransparent supporting surface 1702 is a glass plate. The exposed sharpedges of the glass plate must be beveled in order to prevent injury tousers. Alternatively, a portion of the bezel can be used to cover thesharp edges. When used in combination with the present background plate2102, the bezel will be provided with cut-outs for the support members2106b-c. In addition, the plate member 2104 will include a bevel edge2146 to accommodate the edge of the bezel, as is illustrated for examplein FIG. 28 to prevent shadowing effects during the scanning of adocument.

The foregoing descriptions of the preferred embodiments of the presentinvention have been presented for purposes of illustration only. Theyare not intended to be exhaustive or to limit the inventions to theprecise forms disclosed. Obviously, many modifications and variationswill be apparent to practitioners skilled in this art. For example, inlieu of injection molded plastic, the chassis are amenable to sheetmetal stamping or other known fabrication techniques. Similarly, anyprocess steps described might be interchangeable with other steps inorder to achieve the same result. The illustrated embodiments werechosen and described in order to best explain the principles of theinventions and their best modes of practical application so as to enableothers skilled in the art to understand the inventions as well as theirvarious embodiments and modifications. It is intended that the scope ofthe inventions be defined by the claims appended hereto and equivalentsthereof.

What is claimed is:
 1. A background plate for use with a document feederand a scanning device, the document feeder including a chassis and thescanning device including a substantially transparent document support,the background plate comprising:a plate member defining a surface areasufficient to cover substantially all of the substantially transparentdocument support; and a plurality of support members mounted on andextending downwardly from the plate member and adapted to support theplate member on the scanning device in spaced relation to thesubstantially transparent document support.
 2. A background plate asclaimed in claim 1, wherein the document feeder feeds documents in afeed direction, the plate member defines a rearward portion and aforward portion in the feed direction, and the rearward portion includesan upwardly curved member.
 3. A background plate as claimed in claim 1,further comprising:an attachment system adapted to secure the backgroundplate to the document feeder chassis in such a manner that thebackground plate can move relative to the chassis.
 4. A background platefor use with a document feeder that feeds documents in a feed directionand a scanning device, the document feeder including a chassis and thescanning device including a substantially transparent document support,the background plate comprising:a plate member defining a rearwardportion and a forward portion in the feed direction; and a plurality ofsupport members extending downwardly from the plate member and adaptedto support the plate member on the scanning device in spaced relation tothe substantially transparent document support, the support memberssupporting the plate member such that the rearward portion of the platemember is separated form the substantially transparent document supportby a first distance, the forward portion of the plate member isseparated from the substantially transparent document support by asecond distance, and the first distance is greater than the seconddistance.
 5. A background plate as claimed in claim 4, wherein the firstdistance is approximately twice the second distance.
 6. A backgroundplate for use with a document feeder and a scanning device, the documentfeeder including a chassis and the scanning device including asubstantially transparent document support, the background platecomprising:a plate member; a plurality of support members extendingdownwardly from the plate member and adapted to support the place memberon the scanning device in spaced relation to the substantiallytransparent document support; and an attachment system, including aplurality of latch elements, adapted to secure the background plate tothe document feeder chassis in such a manner that the background platecan move relative to the chassis.
 7. A background plate as claimed inclaim 6, wherein the chassis includes a plurality of protuberances andthe latch elements are configures such that they deflect when passingover protuberances.
 8. A background plate as claimed in claim 6, whereinthe chassis includes a plurality of protuberances, at least one of theprotuberances defines a predetermined size, and at least one of thelatch elements defines an aperture larger than the predetermined size.9. A background plate for use with a document feeder including achassis, comprising:a plate member; an attachment system adapted tosecure the background plate to the document feeder chassis; andanti-static means for preventing static buildup on the plate member. 10.A background plate as claimed in claim 9, wherein the plate member isformed from plastic and the anti-static means comprises an anti-staticadditive to the plastic.
 11. A background plate for use with a documentfeeder including a chassis, comprising:a plate member; an attachmentsystem adapted to secure the background plate to the document feederchassis; and a grounding post secured to the plate member to preventstatic buildup on the plate member.
 12. An automatic document feeder foruse with a scanning device including a substantially transparentdocument support, the automatic document feeder comprising:a chassisadapted to be secured relative to the scanning device; a plate membersecured to the chassis defining a surface area sufficient to coversubstantially all of the substantially transparent document support; anda plurality of support members mounted on and extending downwardly fromthe plate member and adapted to support the plate member on the scanningdevice in spaced relation to the substantially transparent documentsupport.
 13. An automatic document feeder as claimed in claim 12,wherein the document feeder feeds a document in a feed direction, theplate member defines a rearward portion and a forward portion in thefeed direction, and the rearward portion includes an upwardly curvedmember.
 14. An automatic document feeder as claimed in claim 12, whereinthe plate member is secured to the chassis by an attachment systemadapted to secure the plate member to the chassis in such a manner thatthe member plate can move relative to the chassis.
 15. An automaticdocument feeder that feeds documents in a feed direction for use with ascanning device including a substantially transparent document support,the automatic document feeder comprising:a chassis adapted to be securedrelative to the scanning device; a plate member secured to the chassis,the plate member defining a rearward portion and a forward portion inthe feed direction; and a plurality of support members extendingdownwardly from the plate member and adapted to support the plate memberon the scanning device in spaced relation to the substantiallytransparent document support, the support members supporting the platemember such that the rearward portion of the plate member is separatedform the substantially transparent document support by a first distance,the forward portion of the plate member is separated from thesubstantially transparent document support by a second distance, and thefirst distance is greater than the second distance.
 16. An automaticdocument feeder as claimed in claim 15, wherein the first distance isapproximately twice the second distance.
 17. An automatic documentfeeder for use with a scanning device including a substantiallytransparent document support, the automatic document feeder comprising:achassis adapted to be secured relative to the scanning device; a platemember secured to the chassis; and a plurality of support membersextending downwardly from the plate member and adapted to support theplate member on the scanning device in spaced relation to thesubstantially transparent document support; and an attachment system,including a plurality of latch elements, adapted to secure the platemember to the chassis in such a manner that the member plate can moverelative to the chassis.
 18. An automatic document feeder as claimed inclaim 17, wherein the chassis includes a plurality of protuberances andthe latch elements are configured such that they deflect when passingover protuberances.
 19. An automatic document feeder as claimed in claim17, wherein the chassis includes a plurality of protuberances, at leastone of the protuberances defines a predetermined size, and at least oneof the latch elements defines an aperture larger than the predeterminedsize.
 20. A background plate for use with a document feeder and ascanning device, the document feeder including a chassis and at leastone feed roller and the scanning device including a substantiallytransparent document support, the background plate comprising:a platemember defining at least one feed roller opening sized to allow the atleast one feed roller to extend therethrough; and a plurality of supportmembers mounted on and extending downwardly from the plate member andadapted to support the plate member on the scanning device in spacedrelation to the substantially transparent document support.
 21. Abackground plate as claimed in claim 20, wherein document feederincludes a pair of feed rollers and the at least one feed roller openingcomprises a pair of feed roller openings.